The current world population of 5.3 billion is expected to double during the next thirty years. The economic and ecological effects of overpopulation have created a need for a reliable method of birth control. It is estimated that up to 1 billion women and/or couples of different socioeconomic status, religious persuasion, cultural background, and individual commitment to fertility control will desire contraceptive services over the next few decades. The development of a diverse range of effective, reliable, safe, and economical contraceptives is needed to meet the diverse needs of these people.
The most popular method of contraception among couples worldwide is tubal sterilization. Current estimates suggest that more than 140 million women of reproductive age to date have relied on sterilization to avoid further pregnancies Minilaparotomy and Pomeroy tubal ligation, a transabdominal procedure, is generally the sterilization method of choice in most developing countries In developed countries, permanent tubal occlusion is most commonly performed using laparoscopy where the fallopian tube is physically occluded using a ring, a clip, or cauterization. It is estimated that about 700,000 laparoscopic sterilization procedures are done annually in the United States and another 9 million are performed elsewhere throughout the world.
Despite its worldwide use and high efficiency (with a failure rate of about 1 percent), tubal sterilization using the transabdominal approach is associated with substantial trauma and discomfort which, in most cases, involves the inconvenience and expense of a hospital stay and carries the risk of complications such as bleeding, infection, bowel perforation, and reaction to the general anesthesia.
Transcervical tubal occlusion has attracted a great deal of interest during the past ten years and is considered a potential alternative to transabdominal sterilization techniques. The major attraction of the transcervical approach is that it utilizes the external access route via the reproductive tract and thus avoids the need for incisional surgery. Potentially, this procedure can be performed on an out-patient basis or in a physician's office with little or no analgesic, at a reduced cost and greater convenience to the patient. Without doubt, such a contraceptive option would be advantageous to women independent of their cultural background and socioeconomic status.
Available tubal blocking systems depend upon mechanical occlusive techniques, chemically or thermally induced tissue damage, and combinations of these techniques.
Among the mechanical occlusive techniques that have been described, the silicone formed-in-place plug ("Ovabloc") is the generally preferred method with an approximately 90% success rate for first attempts. Less efficient is the P block system that suffers from plug expulsion. Both methods are time-consuming and require highly skilled physicians and sophisticated equipment. The "Ovabloc" method, moreover, is limited by the lack of clinical data on the biological effects of silastic rubber on the fallopian tube.
Chemical agents that induce tissue damages and encourage scarification have been issued to promote the occlusion of the fallopian tube by scarification. Chemical tubal sclerosing agents investigated include substances such as quinacrine, iodine and methylcyanoacrylate. Two major drawbacks in using these sclerosing agents are the need for repeated applications, and the lack of proper biosafety and biocompatibility testing.
Thermal blocking systems use either heat or cryogenic methods to damage tissue and induce the formation of scar tissue to seal the opening of the fallopian tube. Ostium damage using lasers, electrocautery, cryosurgery, and heated water has been described. However, these methods have been found to be unsatisfactory due to their high failure rates (ranging from 11% up to 76%) and the occurrence of major complications, such as excessive uterine bleeding and perforation of the bowel.
Electrocautery methods have generally been found unsatisfactory because they have resulted in insufficient tissue damage, allowing for the regeneration of tubal patency. Methods damaging the tissue at the ostium have difficulty in definitively sealing the entrance to the fallopian tube because of the curvature of the site and the thickness of the tissue at the ostium and the intramural portion of the fallopian tube. Methods that damage tissue along the length of the fallopian tube have been unsatisfactory because they have generally been limited to causing damage to a short segment of the interior mucosal tissue of the fallopian tube. Since the mucosal layer has very efficient regenerative abilities, the damaged fallopian tube will repair itself in a large number of cases. Concerns regarding the regeneration of tubal patency have been addressed by combining the effects of thermal injury with chemical sclerosing agents or mechanical occlusive techniques.
In addition, conventional electrocautery devices have heated the tissue by applying a voltage across two electrodes in contact with the tissue. The resistance of the tissue impedes the flow of electrons, thereby heating the tissue. The first electrode with a small surface area is placed in the fallopian tube and the second electrode, a dispersive patch, is placed on the skin outside of the patient's body. The heat generated is directly related to the current density. Resistive heating occurs at the electrode with the smallest surface area in contact with the tissue and hence the largest current density. Using such systems can result in burns to internal organs, particularly the bowel. Furthermore, as heating takes place and the tissue composition changes due to heating, the resistance of the tissue changes as well. If the tissue reaches 100.degree. C. blood coagulation and other tissue damage will occur, thus requiring very careful monitoring of the procedure during the heating process.
Thus, there exists a need for an inexpensive, easy to perform, reliable method of female sterilization that is void of significant side effects or complications.
It is an object of the present invention to provide a surgical method for female sterilization which is relatively simple to perform, safe, effective, surgically reversible, and inexpensive.
Another object of the present invention is to provide heat directly to the tissue rather than to use the resistance of the tissue to generate heat.
Yet another object of the present invention is to provide a transcervical method of sterilization which is less traumatic to the patient than minilaparotomy or laparoscopic surgery.